Fluid pump

ABSTRACT

There is proposed an embodiment of an electric fluid pump of a semi-axial design wherein support ribs ( 31 ) are arranged between a radially outer pump housing portion ( 32 ) and a first, radially inner motor housing portion ( 8 ) that radially surrounds the electric motor ( 1 ), wherein the radially outer pump housing portion ( 32 ) is formed integrally with the first motor housing portion ( 8 ) and the support ribs ( 31 ). 
     In this manner, as compared to previously known embodiments, small wall thicknesses of the pump housing can be realized because the support ribs will offer sufficient strength. Thus, the number of component parts and the weight can be reduced.

This is a National Phase Application in the United States of International Patent Application No. PCT/EP2006/009761 filed Oct. 10, 2006, which claims priority on German Patent Application No. 10 2005 054 026.0, filed Nov. 10, 2005. The entire disclosures of the above patent applications are hereby incorporated by reference.

FIELD OF THE INVENTION

The invention relates to a fluid pump for internal combustion engines, comprising an electric motor including a rotor arranged in a motor housing, and a stator, the rotor being arranged at least on a drive shaft for common rotation therewith, an impeller fastened to the drive shaft, at least one guide wheel arranged downstream of the impeller in the flow direction of the fluid to be conveyed, and a pump housing surrounding the motor housing, the impeller and the guide wheel, with a pressure socket and an intake socket being arranged opposite the pump housing on the axial ends, support ribs arranged between a radially outer pump housing portion and a first radially inner motor housing portion radially surrounding the electric motor, the radially outer pump housing portion being formed integrally with the motor housing portion and the support ribs.

BACKGROUND OF THE INVENTION

Fluid pumps for internal combustion engines are used particularly as coolant pumps in a cooling circuit. While, in the past, there existed a direct coupling to the rotational speed of the engine and the pumps were driven with the aid of belt and chain drives, more-recent engines are increasingly equipped with rotational-speed-controlled coolant pumps comprising a slit tube so as to render possible a modern heat management. Thus, excessive conveying performance can be prevented, thus allowing e.g. for faster warm-up of the internal combustion engine after cold starting. The delivery volume can be controlled corresponding to the actually required cooling performance.

A pump of the above type is known e.g. from MTZ No. 11, Vol. 2005 (pp. 872-877). The electric coolant pump is provided with an EC motor as a drive aggregate and comprises a pump head with axial inlet and tangential outlet. However, the components and particularly the housing portions used in the pump are very large in view of the power intake of the pump, thus requiring the use of a relatively large drive motor.

Thus, disclosed in US 2002/0106290 A1 is an electric fluid pump of a semi-axial design wherein the electric motor, although having the same power intake, can be smaller-sized while reaching higher rotational speeds, thus making it possible to reach the same delivery volumes although using a pump of a smaller size. The motor is a fully encased electric motor with a guide wheel arranged on its outside. However, downstream of the guide wheel when seen in the flow direction, obstacles exist which make it difficult to effect the passage of the electric contacts to the electronics unit. On the side of the impeller, the whole motor is sealed towards the environment by sealing means. It is at least debatable in how far such a sealing means will be sufficiently effective on rotating components.

The pump housing is of a two-part design and comprises various stepped portions and through holes for electric contacts. Depending on the desired maximum delivery quantity, it will be necessary to design different electric motors and housings. Due to the relatively short guide vanes, it appears unlikely that a complete elimination of twist can be obtained. Further, the pressure loss caused by the passage of the electric contracts is relatively high so that the gain with respect to the power intake of the electric motor will be partly thwarted by the pressure losses occurring.

From FR 2 222 885, there is known a semi-axial pump comprising a multi-part housing of which the central portion surrounds the electric motor and serves a one-part motor and pump housing, wherein the pump housing is connected to the motor housing via support ribs. Downstream of these housing portions in flow direction, the electric contacts are guided to the outside via additional tubes.

Known from DE 202 01 183 U1 is an axial pump which likewise comprises a one-pieced motor and pump housing portion. Electric contacts leading to the outside are not disclosed.

In both of the above pumps, the support ribs are of a linear shape and thus do not serve as a guide wheel for reducing the occurring twist. Instead, high pressure losses will occur because the energy of the tangential component of the flow is nearly completely converted to frictional losses.

Thus, it is an object of the invention, while keeping the delivery volume on the same amount, to reduce the size of the pump and thus also of the electric motor and to avoid pressure losses, i.e. to increase the efficiency of the pump. Further, the weight of the pump and the number of its component parts shall be reduced.

SUMMARY OF THE INVENTION

The above object is achieved in that the support ribs have a shape making them suitable for use as a guide wheel of the fluid pump, and have a width allowing an electric contact element to be guided from an electronics unit to a stator winding via a bore formed in one or a plurality of the support ribs. In this manner, the support ribs will take over the additional function of converting the tangential flow component into an axial flow component without causing higher pressure losses. The efficiency is increased and the number of component parts is reduced. By the fact that the electric contacts are passed through the ribs, the flow resistance is reduced and the efficiency of the pump is increased because of the absence of internal component parts in the flow path. In comparison to known embodiments, it is possible to reduce the wall thickness of the pump housing because the support ribs will offer sufficient strength. The number of component parts and the weight are reduced.

According to a further embodiment, the radially outer portion of the pump housing is of a cylindrical shape so that the connection to a suction-side pump housing portion and a pressure-side pump housing portion can be easily established and only slight losses will occur.

According to a particular embodiment, a suction-side pump housing portion, flaring in the flow direction, is formed integrally with a housing portion of a valve arranged upstream thereof. Thus, it is rendered possible to realize a modular design comprising upstream bypass or thermostat valves, again allowing for a reduction of the number of component parts and the weight.

Preferably, the first portion of the motor housing is arranged to delimit the electric motor on the suction side. Nonetheless, production—e.g. by aluminum pressure die casting—can be performed at low costs, again allowing for a reduced number of component parts, keeping the risk of corrosion low and reducing the danger of faults in assembly.

Thus, there is provided a fluid pump which has a small number of component parts and a low weight, is easily assembled and is less susceptible to flow losses and thus has a higher efficiency as compared to known pumps.

An embodiment of a fluid pump of the invention is illustrated in the drawing and will be described hereunder.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE shows a sectional lateral view of a fluid pump of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The fluid pump shown in the FIGURE, which is useful particularly as a coolant pump in internal combustion engines, is driven by an electronically commutated electric motor 1 comprising a stator 2 and a rotor 4 arranged on a drive shaft 3. Arranged on the axial end of drive shaft 3 is an impeller 5 which is of a semi-axial design and which by its rotation will convey the to-be-conveyed fluid, particularly a coolant, from a suction socket 6 substantially axially through the fluid pump to a pressure socket 7.

The electric motor 1 is accommodated in a motor housing consisting of a first motor housing portion 8 on the suction side and a second motor housing portion 9 on the pressure side. Extending through the suction-side motor housing portion 8 is the drive shaft 3 having the impeller 5 arranged thereon. For this purpose, the suction-side motor housing portion 8 is formed with a bore 10 having arranged therein a first bearing 11 for support of drive shaft 3. Behind the first bearing 11 when viewed from the suction side, a ceramic axial slide bearing 12 as well as a rubber sleeve 13 and a spacer 14 are arranged. By means of this configuration, a sufficiently vibration-damped support of the impeller side of drive shaft 3 of electric motor 1 is obtained. The spacer serves for extending the distance between the first bearing 11 and a second bearing 15, allowing a better compensation for an angle error when forming the bore 10 for accommodating the bearings. Again downstream of spacer 14, a rotor plate pack 16 is arranged on the shaft, which pack is formed with axial slits for accommodating magnets 17 which cooperate with a stator coil 18 in a known manner. The rotor 4 is axially and radially delimited by a capsule 19. The stator coil 18 is wound onto an insulating body 20 and delimits a stator plate pack 21 in a known manner. For closing the magnetic circuit, the stator plate pack 21 is connected in a form-closed manner to a magnetic-yoke 22. The magnetic-yoke 22 is arranged to bear against an abutment portion 23 formed on an inner face of the first, suction-side motor housing portion 8.

Rotor 4 is separated from stator 2 by a slit tube 24 which on the suction side of the pump is arranged to rest in a corresponding receiving opening 25 of the suction-side motor housing portion 8 and which has also its opposite axial end arranged in a corresponding receiving opening 26 of the pressure-side motor housing portion 9. Thus, the stator 2 with its sensitive coil 18 is arranged in a dry space which is separated by the two motor housing portions 8 and 9 and by the slit tube 24.

Provided on the pressure-side end of the slit tube 24 is a closure member 27 having arranged therein the second bearing 15 for supporting the drive shaft 3. Axially, the closure member 27 is secured by the pressure-side motor housing portion 9 which with an interposed sealing member 28 is arranged in an accommodating opening 29 of the suction-side motor housing portion 8.

The contacting of the stator coil 18 is effected via a bore 30 in a radial direction through the pressure-side motor housing portion 9. To avoid possible flow losses caused by such additional inserts as has been known in the state of the art, the bore is passed through support ribs 31 which are required for sufficient strength and attachment of a pump housing. For this purpose, the support ribs 31 have a sufficient width and are arranged in a sort of airfoil configuration so as to preclude a narrowing of the cross section. Via this bore 30, it is now possible to guide an electric contact element, not illustrated, to an electronics unit, also not illustrated, for the controlling of motor 1.

In the illustrated embodiment, the support ribs 31 are formed to the effect that they also serve as a guide wheel, thus obviating the need for an additional guide wheel directly behind impeller 5. This makes it possible to produce the suction-side motor housing portion 8 together with the support ribs and a cylindrical, radially outer pump housing portion 32 in a simple manner as one integral unit. The pump housing portion 32 surrounds the radial inner motor housing portion 8 as well as the complete electric motor 1.

On the downstream and the upstream side of the housing portion 8,31,32, two identical pump housing portions 33,34 are fastened by a screw connection, each time with an interposed sealing means 50. The suction-side pump housing portion 33, flaring in the flow direction, comprises the suction socket 6 configured as a cylindrical portion 35 with an adjoining flaring portion 36. In the transition region 37 between the first portion 35 and the second portion 36, the semi-axial impeller 5 of the fluid pump is arranged. In the present embodiment, the flaring portion 36 is adjoined by a further, short cylindrical portion 38 of a larger diameter to provide for a smooth transition to the cylindrical pump housing portion 32.

Also the pressure-side pump housing portion 34 comprises corresponding portions narrowing in the flow direction, as well as cylindrical portions; due to the identity of these component parts, they are provided with the same reference numerals.

Further, the identical pump housing portions 33,34 are formed with grooves 39 engaged by radial ends 40 of return vanes 41. These return vanes 41 serve as a post-guidance structure 42 which is effective to generate a completely twist-free flow behind the pressure socket 7. The post-guidance structure 42 is formed on a surface 43 of the pressure-side motor housing portion 9 and becomes necessary because the support ribs 31 serving as a guide wheel are relatively short and a complete reduction of the twist will normally not be accomplished in this region of the fluid pump. Further, the pressure-side motor housing portion 9 can be produced from plastic while the suction-side motor housing portion should, if possible, be produced from aluminum and thus is expensive. If the guide wheel were arranged in this region, this would necessitate a relatively expensive production process whereas the manufacture of the post-guidance structure on the plastic housing portion 9 is simple and inexpensive.

The grooves 39 are also effective to define the position of the pressure-side pump housing portion 34 relative to the pressure-side motor housing portion 9. When, during the assembly of the pump, the screws are tightened for fastening the pressure-side pump housing portion 34 to the cylindrical pump housing portion 32, the pressure-side pump housing portion 34 will press the motor housing portion 9 via the return vanes 40 against the motor housing portion 8 and respectively into the accommodating openings 29 of motor housing portion 8. Further, thereby, the motor housing portion 9 will be pressed against the closure member 27 and respectively against the split tube 24 so that no additional attachment of the two motor housing portions 8,9 will be required.

During operation of the pump, the rotation of impeller 5 comprising a plurality of impeller vanes 44 has the effect that the to-be-conveyed fluid or particularly coolant will be conveyed through the space between the pump housing 32,33,34 and the motor housing 8 and 9, and will then be conveyed past the support ribs 31 where—due to their function as a guide wheel—already a part of the twist will be eliminated from the flow, and will further be conveyed via the post-guidance structure 42 wherein the flow will be completely freed of the existing twist, so that the applied energy can be as largely as possible converted into pressure energy and thus into an axial flow without occurrence of frictional losses.

Behind impeller 5, part of the fluid will flow through bores 45 formed in the suction-side motor housing portion 8. A further part of the fluid will flow behind impeller 5 all the way to the drive shaft 3 and, in this region, onward between the first bearing 11 and the drive shaft 3 so that the existing slide bearing will receive sufficient lubrication. Thus, coolant liquid has reached the rotor space, which coolant in turn will be passed on—between drive shaft 3 and second bearing 15 and via non-visible bores of closure member 27—into a space 46 axially downstream thereof. The space 46 is connected, via a further bore 47 axially extending through the pressure-side motor housing portion 9, to the space arranged therebehind. Thus, what is accomplished is a lubrication of the bearings 11,15 as well as a possibility for cooling and for discharge of possible air quantities in the rotor space.

This semi-axial pump is distinguished particularly by the possibility to give it a quite small constructional size because, in comparison to known pumps, it is rendered possible, on the basis of the same power input, to obtain the same delivery rate with a reduced motor size and increased rotational speed. This is accomplished particularly by the extremely reduced pressure losses in such a construction; also, however, by the semi-axial design.

Further, a pump of the above type is very inexpensive in production because there is involved a reduced number of different constructional parts. This will in turn reduce possible errors in the assembly process. Due to the absence of an additional guide wheel and due to the integration of the electric contacts into the support ribs, the need for additional constructional parts is avoided and pressure losses are reduced. Generally, thus, a higher efficiency is reached.

Of course, the simple configuration of the pump housing portions 33,34 offers the possibility to provide them with a flange arranged on the pressure socket and the suction socket, respectively. This makes it possible, on the one hand, to establish a direct connection to the motor housing or, on the other hand, to switch a plurality of pumps in series so as to increase the conveyed fluid volume. This is made possible especially by the twist-free flow effected by the post-guidance structure 42, allowing the flow to be passed directly to the impeller 5 of a downstream pump without occurrence of energy losses. Thus, in cases where twice the usual performance is required, it will not be necessary to build a larger pump which in turn would have a larger motor; instead, because of the similarity of the component parts, it is possible to simply arrange the corresponding required number of pumps in series.

Further, because of the simple design particularly of the suction-side pump housing portion 33, the possibility exists to produce the latter integrally with valve housing portions so that the pump housing portion 33 can comprise e.g. a receiving portion to accommodate a bypass or an integrated thermostat valve. Also parts of the housing of a sliding cylindrical valve can be produced integrally with the suction-side pump housing portion 33.

It is understood that the illustrated exemplary embodiment represents merely one possible realization of the invention and that various aspects of the design of this embodiment can be modified without leaving the protective scope of the claims. 

1. A fluid pump for internal combustion engines, comprising: an electric motor including a rotor arranged in a motor housing, and a stator, wherein the rotor is arranged at least on a drive shaft for common rotation therewith; an impeller fastened to the drive shaft; at least one guide wheel arranged downstream of the impeller in a flow direction of fluid to be conveyed; and a pump housing surrounding the motor housing, the impeller and the guide wheel, wherein the pump housing is provided with a pressure socket and an intake socket arranged opposite the pump housing on axial ends, and support ribs are arranged between a radially outer pump housing portion and a first, radially inner motor housing portion that radially surrounds the electric motor, wherein said radially outer pump housing portion is formed integrally with said motor housing portion and the support ribs, wherein the support ribs are shaped so that the support ribs serve as a guide wheel of the fluid pump, and the support ribs have a width so that an electric contact element is guidable from an electronics unit to a stator winding via a bore formed in one or a plurality of the support ribs.
 2. The fluid pump for internal combustion engines according to claim 1, wherein that the radially outer pump housing portion is of a cylindrical shape.
 3. The fluid pump for internal combustion engines according to claim 1, wherein that a suction-side pump housing portion flaring in the flow direction is formed integrally with a housing portion of a valve arranged upstream thereof.
 4. The fluid pump for internal combustion engines according to claim 1, characterized in that the first motor housing portion is arranged to delimit the electric motor on the suction side.
 5. The fluid pump for internal combustion engines according to claim 2, wherein a suction-side pump housing portion flaring in the flow direction is formed integrally with a housing portion of a valve arranged upstream thereof.
 6. The fluid pump for internal combustion engines according to claim 2, characterized in that the first motor housing portion is arranged to delimit the electric motor on the suction side.
 7. The fluid pump for internal combustion engines according to claim 3, characterized in that the first motor housing portion is arranged to delimit the electric motor on the suction side. 